The following patents are believed to be relevant to the subject matter of this application:
U.S. Pat. Nos. 5,201,881; 5,011,497; 4,279,041; 5,080,675; 4,650,491; 3,938,198; 4,292,695; 4,624,674; 2,765,787; 4,735,625; 5,370,699; 5,641,323; 5,323,765; 5,658,345; 3,875,594; 3,938,198; 4,292,695; 4,344,193; 4,570,270; 4,650,491; 4,279,041; 4,661,112; 4,662,889; 4,664,668; 4,715,859; 4,795,470; 4,795,474; 4,808,186; 4,813,962; 4,822,365; 4,888,020; 4,904,269; 4,908,035; 4,919,674; 4,919,678; 4,936,856; 4,938,771; 4,938,773; 4,950,298; 4,955,912; 4,955,919; 4,963,153; 4,963,154; 4,997,447; 5,002,581; 5,019,107; 5,041,140; 5,049,393; 5,080,677; 5,108,446; 5,108,451; 5,116,374; 5,133,763; 5,146,933; 5,417,406; 5,151,521; 5,156,631; 5,171,276; 5,181,925; 5,197,987; 5,197,989; 5,201,881; 5,201,881; 5,217,498; 5,217,499; 5,222,985; 5,282,868; 5,290,314; 5,314,478; 5,314,494; 5,316,550; 5,326,376; 5,330,534; 5,314,493; 5,336,268; 5,344,459; 5,358,525; 5,370,699; 5,376,064; 5,376,125; 5,387,244; 5,389,107; 5,405,403; 5,405,411; 5,415,662; 5,425,779; 5,448,489; 5,458,643; 5,458,651; 5,480,311; 5,491,882; 5,507,814; 5,507,818; 5,507,820; 5,507,823; 5,507,830; 5,507,833; 5,507,836; 5,514,182; 5,514,184; 5,522,904; 5,507,835; 5,246,461; 5,364,839; 5,376,120; 5,393,739; 5,480,449; 5,510,418; 5,522,894; 4,892,551; 5,660,225; 4,089,071; 5,281,226; 5,443,383; 5,480,437; 5,032,134; 4,997,444; 5,002,579; 5,443,512; 5,133,762; 5,080,678; 5,944,759; 5,944,758; 5,944,757; 5,944,756; 5,938,702; 5,935,174; 5,935,175; 5,935,173; 5,935,172; 5,935,171; 5,931,871; 5,931,870; 5,928,289; 5,928,288; 5,928,287; 5,928,286; 5,928,285; 5,910,236; 5,916,270; 5,916,269; 5,916,268; 5,913,858; 5,911,759; 5,911,758; 5,910,172; 5,910,171; 5,906,644; 5,906,643; 5,906,210; 5,904,720; 5,904,688; 5,902,340; 5,882,206; 5,888,204; 5,879,407; 5,879,405; 5,879,404; 5,879,402; 5,879,401; 5,879,398; 5,879,397; 5,879,396; 5,879,395; 5,879,393; 5,879,392; 5,879,390; 5,879,387; 5,871,548; 5,871,547; 5,824,108; 5,824,107; 5,824,103; 5,824,102; 5,824,101; 5,824,098; 5,800,560; 5,800,558; 5,800,557; 5,800,555; 5,800,554; 5,800,553; 5,788,704; 5,782,928; 5,782,925; 5,776,202; 5,766,260; 5,766,257; 5,755,811; 5,755,810; 5,755,804; 5,755,801; 5,755,799; 5,743,918; 5,910,172; 5,211,666; 5,507,832; 4,433,440; 5,397,359; 5,507,834; 5,314,492; 5,405,394; 5,316,550; 5,314,494; 5,413,610; 5,507,835; 5,373,621; 5,433,750; 3,879,767; 5,376,123; 5,480,437; 3,576,133; 5,376,126; 5,496,375; 3,600,718; 5,108,449; 5,507,817; 5,181,929 and 5,507,829.
Foreign patents DE 2,247,721; EP 0,308,081; GB 2,126,096; GB 2,069,338; EP 0,190,446; EP 0,066,092 and EP 0,253,941.